WDPN31 PGTW 060300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (AERE) WARNING 
NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.4N 138.8E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 122 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EASTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AT THE PRESENT TIME THE ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS WEAK CYCLONIC CURVATURE ON THE NORTHERN EDGE OF A
BROAD DISORGANIZED CONVECTIVE SYSTEM SOUTH OF IZU PENINSULA. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A
060021Z METOP-B ASCAT PASS. THE OVERALL CIRCULATION IS RELATIVELY
WEAK YET THERE IS A DECENT SIGNATURE OF CYCLONIC CURVATURE ON THE
EAST SIDE WHICH LENDS INCREASED LEGITIMACY TO THE DATA. IN ADDITION
TO TD 05W, ANIMATED MSI ALSO SHOWS THERE IS A WELL DEFINED
CIRCULATION CENTER TO THE NORTHEAST OFF THE EAST COAST OF HONSHU.
THE INITIAL INTENSITY OF 25 KNOTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AFOREMENTIONED ASCAT PASS, WHICH IS
SLIGHTLY LOWER THAN THE CIMSS ADT ESTIMATE OF 32 KNOTS. THE CURRENT
ENVIRONMENT IS UNFAVORABLE FOR TROPICAL CYCLONE DEVELOPMENT. SEA
SURFACE TEMPERATURES ARE ABOVE 26C BUT WIND SHEAR IS HIGH, YET THE
UPPER LEVEL DIVERGENT FLOW AND THE POSITIVE VORTICITY ASSOCIATED
WITH A 500MB TROUGH ARE PROVIDING JUST ENOUGH ENERGY FOR THE
CIRCULATION TO MAINTAIN ITSELF.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP LAYER
SUBTROPICAL RIDGE (STR) TO THE SOUTH 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS ADT: 32 KTS AT 052340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE EASTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TD 05W IS ANTICIPATED TO CONTINUE MOVING TO
THE EAST BEFORE MERGING WITH THE AREA OF LOW PRESSURE CURRENTLY
DEVELOPING EAST OF HONSHU WITHIN THE NEXT 12-18 HOURS. AS THE TWO
AREAS MERGE THEY WILL BE IN AN AREA OF MAXIMUM BAROCLINIC FORCING
AHEAD OF A 500MB SHORTWAVE TROUGH AND UNDER STRONG 200MB DIVERGENT
FLOW. THE SYSTEM IS THEN EXPECTED TO QUICKLY INTENSIFY TO A PEAK OF
35 KNOTS BY TAU 24. BY TAU 36 THE 500MB TROUGH PINCHES OFF INTO A
LOW HEIGHT CENTER WHILE REMAINING WARM CORE BAROTROPIC. TD 05W THEN
BECOMES VERTICALLY STACKED UNDER THIS 500MB LOW AND WILL BEGIN TO
TRANSITION FROM TROPICAL TO SUBTROPICAL IN NATURE. BY TAU 48 THE
SYSTEM IS FORECAST TO BECOME QUASI-STATIONARY AS THE STEERING
ENVIRONMENT BECOMES WEAK, AS A RESULT OF A REX BLOCK TO THE NORTH.
WHILE THE SYSTEM IS QUASI-STATIONARY IT WILL BEGIN TO SLOWLY WEAKEN
DUE TO DRY AIR ENTERTAINMENT, UPWELLING OF COOLER WATERS BELOW 24C
AND MODERATE UPPER-LEVEL SUBSIDENCE. THE SYSTEM IS EXPECTED TO
BECOME FULLY SUBTROPICAL BY TAU 36. BY TAU 72 THE REX BLOCK IS
FORECAST TO BREAK DOWN AND THE STR REORIENT TO A NORTH SOUTH AXIS
TO THE EAST OF THE SYSTEM, WHICH WILL EJECT TD 05W SHARPLY TO THE
NORTH. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT IN THE FIRST 12-24 HRS AS THE SYSTEM TRACKS EAST BEFORE
MOVING IN A EAST TO SOUTHEASTERLY DIRECTION FROM 24-48. BY TAU 48
ALL GUIDANCE SUGGESTS A QUASI-STATIONARY LOOPING MOTION. WHILE THE
FORECAST TRACK REMAINS STRAIGHT, THE TRACK COULD IN FACT LOOP BACK
IN A COUNTERCLOCKWISE MANNER. THE MODELS SHOW HIGH UNCERTAINTY IN
THE EXACT TRACK FROM 48-72 HRS AS THE SYSTEM MEANDERS IN THE WEAK
STEERING ENVIRONMENT. HENCE THERE REMAINS SOME UNCERTAINTY IN THE
JTWC FORECAST DUE TO THE ERRATIC MOTION. ALL GUIDANCE SUGGESTS A
NORTHWARD TRACK BY TAU 72. THE FORECAST REMAINS CONSISTENT WITH THE
PREVIOUS FORECAST AND LIES ON THE NORTH AND EASTERN SIDE OF THE
GUIDANCE ENVELOPE. CONFIDENCE IS LOW, DUE TO THE UNCERTAINTIES IN
THE INITIAL POSITION AND THE TIMING OF THE QUASI-STATIONARY MOTION
AS WELL AS THE STRENGTH OF THE POLEWARD TURN. INTENSITY GUIDANCE IS
IN GOOD AGREEMENT WITH ALL MODELS CONSTRAINED WITHIN A 5 KNOT
ENVELOPE THROUGH THE DURATION OF THE FORECAST.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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